1. Field of the Invention
The present invention relates to a template for drawing a plurality of concentric figures, and more particularly to a template for drawing similar figures concentrically.
2. Description of the Prior Art
Templates for use in drawing figures are normally in the form of a thin plastic panel having differently shaped and sized holes defined therein. When a certain figure is to be drawn using a template, the edge of a corresponding hole of the template is followed with a pencil, a pen, or the like which is being pressed against a drawing sheet. Such templates are useful in drawing various figures such as computer program flowchart symbols, circles, ellipses, triangles, squares, and other shapes, exactly alike, without making actual dimensional measurements.
Conventional templates typically have horizontal reference lines inscribed thereon on lateral sides of each hole so that a figure to be drawn can be positioned with respect to a certain frame, and also vertical reference lines inscribed thereon on upper and lower sides of each hole. When a figure is to be drawn in a given position on a graph paper sheet, the horizontal reference lines on the lateral sides of a desired hole in the template are held in alignment with one of the horizontal lines on the graph paper sheet, and then the vertical reference lines on the upper and lower sides of the hole are aligned with one of the vertical lines on the graph paper sheet. Thereafter, the inner edge of the hole is traced with a pencil, a pen, or the like.
When a next figure, which is similar to the figure thus drawn, is to be drawn concentrically therewith, the horizontal reference lines on the, lateral sides of a template hole corresponding to the next figure are aligned with the previously selected horizontal line on the graph paper sheet, and the vertical reference lines on the upper and lower sides of the next figure hole are brought into alignment with the previously selected vertical line on the graph paper sheet. Then, the next figure is drawn inside or outside of the previously drawn figure while following the edge of the next figure hole in the template.
The horizontal and vertical reference lines inscribed on the conventional templates are relatively short. Figures may not be drawn accurately, using the conventional templates, because of an optical illusion caused by the thickness of the templates and shadows produced by the templates under illuminating light applied obliquely thereto. Therefore, a considerable degree of caution and skill is required on the part of the draftsman in order to align the reference lines on the templates with given lines on graph paper sheets.
Double concentric circles are to be drawn with a spacing of 0.5 mm, for example. If the centers of these two circles are positionally diplaced from each other by 0.2 mm because the draftsman is not careful or skillful enough, then the two circles are spaced from each other by 0.3 mm at minimum and 0.7 mm at maximum, and hence cannot be acceptable as properly drawn double concentric circles.